光谱技术结合BiPLS-GA-SPA和ELM算法的生菜冠层氮素含量检测研究

氮素是影响生菜产量和品质的重要因素，光谱技术是检测作物氮素含量最有效的手段之一。通过获取不同氮素水平下生菜冠层的反射光谱，对其进行FDSGF（first-order derivative based savitzky-golay filt）滤波后，利用后向区间偏最小二乘算法（BiPLS）、遗传算法（GA）及连续投影算法（SPA）对特征波长进行梯度提取，最终从2 151个波长点中提取了8个与生菜氮素最为相关的特征波长。分别利用多元线性回归（MLR）、径向基函数神经网络（RBFNN）及极限学习机（ELM）三种算法建立了基于特征波段或特征波长的8个生菜冠层氮素含量检测模型。结果表明： BiPLS-GA-SPA-ELM模型（RMSEC=0.241 6%，R_c=0.934 6，RMSEP=0.284 2%，R_p=0.921 8）的预测结果优于其他模型，为指导合理施肥和开发便携式仪器提供了理论基础。

Measurement of Nitrogen Content in Lettuce Canopy Using Spectroscopy Combined with BiPLS-GA-SPA and ELM

Nitrogen fertilizer is necessary to improve yield and quality of lettuce .Spectroscopy is one of the most effective tech-niques used to detect crop nitrogen content .In this study ,canopy reflectance spectra were acquired under five levels of nitrogen , and then were Savitzky-Golay smoothed ,the first-order derivative spectra were calculated from the smoothed spectra to eliminate noise effects .Backward interval partial least squares (BiPLS ) ,genetic algorithm (GA ) and successive projections algorithm (SPA) were combined to select the efficient wavelengths .The number of variables was decreased from 2 151 to 8 .The optimal intervals or variables were used to build multivariable linear regression (MLR) model ,radial basis function neural network (RBFNN) models and extreme learning machine (ELM ) models .This work proved that the results of BiPLS-GA-SPA-ELM model was superior to others with RMSEC was 0.241 6% ,Rc was 0.934 6 ,RMSEP was 0.284 2% and Rp was 0.921 8 .Our research results may provide a foundation for nutrition regulation and developing instrument .